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Revisor number: R-04740

The Minnesota Pollution Control Agency (MPCA) plans to amend Minnesota Rules (Minn. R.) chapter 7050, which establishes beneficial uses and water quality standards (WQS) to protect those uses, and designates where the uses occur in waters of the state. The planned amendments, also referred to as the Lakes WQS rulemaking, affect Class 2 beneficial uses, which protect surface waters for aquatic life and recreation. This rulemaking’s main proposals are to:

  1. Revise the lake eutrophication standards for northern lakes.
  2. Revise the lake eutrophication standards and list of waters designated for the protection of cold-water lake habitat.
  3. Adopt a tiered aquatic life uses (TALU) framework for lakes.

We also intend to make several housekeeping changes to Minn. R. chapter 7050 to bring the protections of aquatic life up to date with current science.

Rulemaking documents


This rulemaking will propose to revise standards and use designations for one use class: Class 2 (surface) waters protected for aquatic life and recreation. The revisions to these standards would largely affect only one aquatic habitat type: lakes. The focus of these revisions to standards are on eutrophication, oxygen, temperature, and biological criteria. This rulemaking also reviews and confirms use designations for cold-water lake habitats and for lakes with exceptional fish communities. The expected rule revisions include:

  • Northern lake eutrophication standards: Revising lake eutrophication standards for the North region (Northern Lakes and Forests and Northern Minnesota Wetlands ecoregions) by dividing cool/warm water lakes into 2 types: mixed (shallow) and stratified (deep). The separate standards acknowledge the natural differences in trophic state between these lake types and bring this region into alignment with the structure of the existing lake eutrophication standards for the Central and South regions.
  • Cold-water habitat standards for lakes: Revising lake eutrophication standards and adding an oxythermal standard to cold-water lake habitats (Class 2A). These revisions will establish separate criteria for lake trout, lake whitefish, cisco, and stream trout lakes, which are specific to the ecological requirements for these fish taxa.
  • Cold-water habitat designations for lakes: Review and confirm the list of lakes designated for the protection of cold-water habitat in Minn. R. 7050.0470. This includes a review of the existing Class 2A lakes and the addition or removal lakes. In addition, the MPCA will propose to add cold-water species designators to the lakes listed in Minn. R. 7050.0470 to clarify which species are protected in each lake.
  • Tiered aquatic life uses (TALU) for lakes: Following the framework develop developed for rivers and streams as a model, these revisions are expected to include a proposal to develop and adopt a tiered aquatic life uses framework for lakes. This framework would adopt General and Exceptional Uses along with the biological criteria to support designation and assessment of these lake categories.
  • Additional housekeeping revisions to support implementation of these rules: Housekeeping revisions include changes to definitions in Minn. R. 7050.0150, listing lake use designations in documents incorporated by reference, and correcting errors in the river eutrophication standards.

Technical support documents

The following draft documents provide technical background for the major elements of the draft lake standards rule.

Projected schedule

This is a tentative schedule.

Sept. 18, 2023Request for comments published in State Register
Fall 2023Informal public engagement
Winter 2023-2024Peer review of technical support documents
Spring 2024Drafting of rule language/Statement of Need and Reasonableness (SONAR)
To be determinedPublic information meeting on draft rule amendments
To be determinedNotice of Intent to Adopt Rules, public comment period and hearing
To be determinedAdoption of rules
To be determinedU.S. EPA review and approval
15396: GovDelivery: Rulemaking WQS Lake aquatic life and recreation MNPCA_491
Envelope and cursor

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